According to J. Med. Chem. 13, 169 (1970) "Compound 26" of the Formula I, of unspecified stereochemical composition, ##STR1## has been obtained as a "by-product in the preparation of 6 and 7", i.e., the erythro and threo "1-(1,4-benzodioxan-2-yl)-2-aminoethanols". According to said publication "compound 26" increases heart rate and inhibits isoproterenol induced tachycardia. Structural Formula I may represent any possible stereoisomers of both the erythro and threo series, i.e., the (SRSR), (RSSR), (SRRS), (RRSS), (RSRR), (SRSS), (RSSS), (SRRR), (RRRR) and (SSSS); the (SRSR) and (RRSS) isomers being the meso-compounds, and the remaining are racemates.
Taking advantage of stereospecific syntheses of intermediates invented by the Applicants' (U.S. Pat. Nos. 4,187,313 and 4,212,808) specific isomers of either the erythro or threo series can now be prepared. Surprisingly it was found that the (SRSR)-meso-compound of Formula II below, belonging to the erythro series, is a superior antihypertensive agent with bradycardic activity.